This update applies to pixhawk only

Also one param name in the code clarified.

With H_ prefix they appear with the rest of the tradheli specific params in the parameter list.

This prevents full negative pitch when touching down in Alt Hold or Auto-Landing.

We need the flash space, and this probably won't work for tradheli anyway since tradheli needs most of the control from Feedforward rather than P term.  And D-term is very very bad.

this also brings GCS_Mavlink.pde closer to the plane implementation

support 3 UARTs on non-AVR platforms

PX4 and SITL get an extra UART

TradHeli: Fix for yaw offset switching.  Yaw Offset should switch on and off with the main motor, not waiting until the rotor has reached full speed.

Loiter's Roll-Pitch mode was not being set on start-up.

we know that packed data structures are not as efficient

this allows for secondary sensors

We now limit the target stopping point to 1x the xy leash length while
previously it was 2x.  This is justified because this limit is only used
when the copter is travelling at higher speeds but at higher speeds air
drag tends to make the copter stop more quickly naturally.